README

NAME

    Time::Zone::Olson - Provides an Olson timezone database interface

VERSION

    Version 0.46

SYNOPSIS

        use Time::Zone::Olson();
    
        my $time_zone = Time::Zone::Olson->new( timezone => 'Australia/Melbourne' ); # set timezone at creation time
        my $now = $time_zone->time_local($seconds, $minutes, $hours, $day, $month, $year); # convert for Australia/Melbourne time
        foreach my $area ($time_zone->areas()) {
            foreach my $location ($time_zone->locations($area)) {
                $time_zone->timezone("$area/$location");
                print scalar $time_zone->local_time($now); # output time in $area/$location local time
                warn scalar localtime($now) . " log message for sysadmin"; # but log in system local time
            }
        }

DESCRIPTION

    Time::Zone::Olson is intended to provide a simple interface to the
    Olson database that is available on most UNIX systems. It provides an
    interface to list common time zones, such as Australia/Melbourne that
    are stored in the zone.tab file, and localtime/Time::Local::timelocal
    replacements to translate times to and from the users time zone,
    without changing the time zone used by Perl. This allows logging/etc to
    be conducted in the system's local time.

    Time::Zone::Olson was designed to produce the same result as a 64 bit
    copy of the date(1) command.

    Time::Zone::Olson will attempt to function even without an actual Olson
    database on Windows platforms by translating information available in
    the Windows registry.

SUBROUTINES/METHODS

 new

    Time::Zone::Olson->new() will return a new time zone object. It accepts
    a hash as a parameter with an optional timezone key, which contains an
    Olson time zone value, such as 'Australia/Melbourne'. The hash also
    allows a directory key, with the file system location of the Olson time
    zone database as a value.

    Both of these parameters default to $ENV{TZ} and $ENV{TZDIR}
    respectively.

 areas

    This method will return a list of the areas (such as Asia, Australia,
    Africa, America, Europe) from the zone.tab file. The areas will be
    sorted alphabetically.

 locations

    This method accepts a area (such as Asia, Australia, Africa, America,
    Europe) as a parameter and will return a list of matching locations
    (such as Melbourne, Perth, Hobart) from the zone.tab file. The
    locations will be sorted alphabetically.

 comment

    This method accepts the name of time zone such as "Australia/Melbourne"
    as a parameter and will return the matching comment from the zone.tab
    file. For example, if "Australia/Melbourne" was passed as a parameter,
    the "comment" function would return "Victoria". For Windows platforms,
    it will return the contents of the Display registry setting. For
    example, for "Australia/Melbourne" using English as a language, it
    would return "(UTC+10) Canberra, Melbourne, Sydney".

 directory

    This method can be used to get or set the root directory of the Olson
    database, usually located at /usr/share/zoneinfo.

 timezone

    This method can be used to get or set the time zone, which will affect
    all future calls to "local_time" or "time_local". The parameter for
    this method should be in the Olson format of a time zone, such as
    "Australia/Melbourne".

 equiv

    This method takes a time zone name as a parameter. It then compares the
    transition times and offsets for the currently set time zone to the
    transition times and offsets for the specified time zone and returns
    true if they match exactly from the current time. The second optional
    parameter can specify the start time to use when comparing the two time
    zones.

 offset

    This method can be used to get or set the offset for all "local_time"
    or "time_local" calls. The offset should be specified in minutes from
    GMT.

 area

    This method will return the area component of the current time zone,
    such as Australia

 location

    This method will return the location component of the current time
    zone, such as Melbourne

 local_offset

    This method takes the same arguments as localtime but returns the
    appropriate offset from GMT in minutes. This can to used as a offset
    parameter to a subsequent call to Time::Zone::Olson.

 local_abbr

    This method takes the same arguments as localtime but returns the
    appropriate abbreviation for the timezone such as AEST or AEDT. This is
    the same result as from a date +%Z command.

 local_time

    This method has the same signature as the 64 bit version of the
    localtime function. That is, it accepts up to a 64 bit signed integer
    as the sole argument and returns the (seconds, minutes, hours, day,
    month, year, wday, yday, isdst) definition for the time zone for the
    object. The time zone used to calculate the local time may be specified
    as a parameter to the "new" method or via the "timezone" method.

 time_local

    This method has the same signature as the 64 bit version of the
    Time::Local::timelocal function. That is, it accepts (seconds, minutes,
    hours, day, month, year, wday, yday, isdst) as parameters in a list and
    returns the correct UNIX time in seconds according to the current time
    zone for the object. The time zone used to calculate the local time may
    be specified as a parameter to the "new" method or via the "timezone"
    method.

    During a time zone change such as +11 GMT to +10 GMT, there will be two
    possible UNIX times that can result in the same local time. In this
    case, like Time::Local::timelocal, this function will return the lower
    of the two times.

 transition_times

    This method can be used to get the list of transition times for the
    current time zone. This method is only intended for testing the results
    of Time::Zone::Olson.

 determining_path

    This method can be used to determine which file system path was used to
    determine the current operating system timezone. If it returns undef,
    then the current operating system timezone was determined by other
    means (such as the win32 registry, or comparing the digests of
    /etc/localtime with timezones in "directory").

 leap_seconds

    This method can be used to get the list of leap seconds for the current
    time zone. This method is only intended for testing the results of
    Time::Zone::Olson.

 reset_cache

    This method can be used to reset the cache. This method is only
    intended for testing the results of Time::Zone::Olson. In actual use,
    cached values are only used if the mtime of the relevant files has not
    changed.

 tz_definition

    This method will return the TZ environment variable (if any) that
    describes a timezone after the "transition_times" have been used. This
    method is only intended for testing the results of Time::Zone::Olson.

 win32_mapping

    This method will return a hash containing the mapping between Windows
    time zones and Olson time zones. This method is only intended for
    testing the results of Time::Zone::Olson.

 win32_registry

    This method will return true if the object is using the Windows
    registry for Olson tz calculations. Otherwise it will return false.

DIAGNOSTICS

    %s is not a TZ file

      The designated path did not have the TZif prefix at the start of the
      file. Maybe either the directory or the time zone name is incorrect?

    Failed to read header from %s:%s

      The designated file encountered an error reading either the version 1
      or version 2 headers

    Failed to read entire header from %s. %d bytes were read instead of the
    expected %d

      The designated file is shorter than expected

    %s is not a time zone in the existing Olson database

      The designated time zone could not be found on the file system. The
      time zone is expected to be in the designated directory + the time
      zone name, for example, /usr/share/zoneinfo/Australia/Melbourne

    %s does not have a valid format for a TZ time zone

      The designated time zone name could not be matched by the regular
      expression for a time zone in Time::Zone::Olson

    There are two transition times for %s in %s, which cannot be coped with
    at the moment. Please file a bug with Time::Zone::Olson

      The transition times are sorted to handle unsorted (on disk)
      transition times which has been found on solaris. Please file a bug.

    Failed to close %s:%s

      There has been a file system error while reading or closing the
      designated path

    Failed to open %s for reading:%s

      There has been a file system error while opening the the designated
      path. This could be permissions related, or the time zone in question
      doesn't exist?

    Failed to stat %s:%s

      There has been a file system error while doing a stat on the
      designated path. This could be permissions related, or the time zone
      in question doesn't exist?

    Failed to read %s from %s:%s

      There has been a file system error while reading from the designated
      path. The file could be corrupt?

    Failed to read all the %s from %s. %d bytes were read instead of the
    expected %d

      The designated file is shorter than expected. The file could be
      corrupt?

    The tz definition at the end of %s could not be read in %d bytes

      The designated file is longer than expected. Maybe the time zone
      version is greater than the currently recognized 3?

    Failed to read tz definition from %s:%

      There has been a file system error while reading from the designated
      path. The file could be corrupt?

    Failed to parse the tz definition of %s from %s

      This is probably a bug in Time::Zone::Olson in failing to parse the
      TZ variable at the end of the file.

    Failed to open %s:%s

      There has been an error while opening the the designated registry
      entry.

    Failed to read from %s:%s

      There has been an file system error while reading from the registry.

    Failed to close %s:%s

      There has been an error while reading or closing the designated
      registry entry

CONFIGURATION AND ENVIRONMENT

    Time::Zone::Olson requires no configuration files or environment
    variables. However, it will use the values of $ENV{TZ} and $ENV{TZDIR}
    as defaults for missing parameters.

DEPENDENCIES

    For environments where the unpack 'q' parameter is not supported, the
    Math::Int64 module is required

INCOMPATIBILITIES

    None reported

BUGS AND LIMITATIONS

    On Windows platforms, the Olson TZ database is usually unavailable. In
    an attempt to provide a workable alternative, the Windows Registry is
    interrogated and translated to allow Olson time zones (such as
    Australia/Melbourne) to be used on Windows nodes. Therefore, the use of
    Time::Zone::Olson should be cross-platform compatible, but the actual
    results may be different, depending on the compatibility of the Windows
    Registry time zones and the Olson TZ database.

    For perl versions less than 5.10, support for TZ environment variable
    parsing is not complete. It should cover all existing cases in the
    Olson time zone database though.

    To report a bug, or view the current list of bugs, please visit
    https://github.com/david-dick/time-zone-olson/issues

SEE ALSO

      * DateTime::TimeZone

      * DateTime::TimeZone::Tzfile

      * DateTime::TimeZone::Local::Win32

      * Time::Local

      * Time::Local::TZ

AUTHOR

    David Dick, <ddick at cpan.org>

LICENSE AND COPYRIGHT

    Copyright 2021 David Dick.

    This program is free software; you can redistribute it and/or modify it
    under the terms of either: the GNU General Public License as published
    by the Free Software Foundation; or the Artistic License.

    See http://dev.perl.org/licenses/ for more information.